Seems only yesterday that the Republican Party’s new young governors, presiding over some of the most important states in the country, were the pride and joy of the GOP.

But that was yesterday, which holds no promise for tomorrow in the volatile politics of today.

A trio of these once-heralded state leaders are now in trouble.

It’s a cautionary tale, one that Democrats as well as Republicans had better heed (copy to Hillary Clinton). For there’s little security for any candidate, however big a lead he or she enjoys, in a time when candidates, actual and potential, are under scrutiny like never before.

Consider the fall of Bob McDonnell, the telegenic governor of Virginia, who in 2012 was on Mitt Romney’s short list of potential vice presidential running mates, someone, in short, with a potential national future ahead.

Then there’s the all too familiar fall of Gov. Chris Christie — a front-runner for the 2016 GOP presidential nomination — as a consequence of his staff’s role in the George Washington Bridge scandal.

Investigations abound.

A blizzard of subpoenas has landed like newly fallen snow on Christie aides, current and former, and on some leading lights of the Port Authority of New York and New Jersey.

It’s the political story of the year, but where it all leads remains a mystery.

Only in New Jersey, right? Maybe not. For out of virginally pure Wisconsin comes a tale more than slightly similar concerning another rising Republican star, Gov. Scott Walker.

A flood of some 27,000 court documents and public and private emails released last week depicted Walker’s staff in the Milwaukee County executive’s office doing banned political work — on county time — to aid Walker’s first campaign for governor.

Some of the similarities are striking. For one, there’s Kelly Rindfleisch, who pleaded guilty to felony misconduct for doing political work while deputy chief of staff in Walker’s county office. Sound familiar?

It should. Bridget Anne Kelly was deputy chief of staff in Christie’s office when she authored the infamous email signaling it was "time for some traffic problems in Fort Lee," apparently to punish the town’s mayor for not supporting Christie’s re-election.

Kelly has refused to comply with subpoenas calling on her for testimony and documents.

But perhaps the most relevant similarity in the Christie-Walker comparison are the questions both face: What did they know and when did they know it?

How they fare politically could well depend on how these questions are answered — possibly even whether either man can avoid the fate of McDonnell.